Third-hand Smoke: Scientists Warn of Exposure to Cigarette Chemicals Where No One Has Smoked in Decades

Cigarette smoke chemicals can contaminate indoor spaces where no one has lit up in decades by traveling through the air, according to a new study that sheds light on how pervasive these harmful substances might be.

Third-hand smoke—the residual chemicals left by cigarette smoke—can linger on clothing and indoor surfaces such as furnishings and enter a building's ventilation system, researchers at Drexel University found. Previous studies have shown it can even get into neonatal intensive care incubators.

Dr. Michael Waring, co-author of the study and associate professor at Drexel's College of Engineering, said in a statement: "While many public areas have restrictions on smoking, including distance from doorways, non-smoking buildings and even full smoking bans on campus for some universities, these smoking limitations often only serve to protect non-smoking populations from exposure to second-hand smoke."

"This study shows that third-hand smoke, which we are realizing can be harmful to health as second-hand smoke, is much more difficult to avoid."

A man smokes a cigarette outside of an office building February 19, 2002 in New York City. A new study has shed new light on the potential health implications of thirdhand smoke. Spencer Platt/Getty Images

The paper came about after a Drexel researcher studied how outdoor air particles change when they come inside, by measuring the air composition in an unoccupied classroom.

Despite it being smoke-free for over two decades, tests revealed that 29 percent of the room's air mass was made up from chemicals found in third-hand smoke.

The team behind the study, published in Science Advances, then simulated third-hand smoke in a lab setting by pumping cigarette smoke into a glass container. The smoke was removed and the container treated with outdoor air. Tests showed levels of third-hand smoke chemicals in the air that came into contact with the container had increased by 13 percent. This suggested that although the container looked smoke-free, the chemicals from the cigarette were able to attach to aerosol particles.

The new study builds on previous evidence showing that third-hand smoke chemicals can even settle on sterile surfaces, and return to the gas phase when exposed to chemicals such as ammonia, which is commonly found in cleaning products.

Air conditioning systems in buildings offer up the perfect environment for this to happen.

Dr. Peter DeCarlo, an atmospheric chemist at Drexel who co-authored the study, explained in a statement: "Aerosol particles are ubiquitous particles suspended in the air—they come from a variety of sources and are known to be detrimental to health."

"The fact that third-hand smoke can attach to them, like it would to the clothing or furniture of a smoker, means that the potentially toxic chemicals associated with third-hand smoke are found in places we wouldn't have expected."

More research is now needed to understand the public health implications of these findings, as well as whether the chemicals present in e-cigarettes have a similar effect.

Professor Neil Thomas of the University of Birmingham's Institute of Applied Health Research who was not involved in the research, told Newsweek there is currently very little data available on the potential harm of third-hand smoke.

"It is also going to be quite hard to study given that for the opportunity in most settings to be exposed to third-hand smoke means there normally would need to have been a smoker in the vicinity and thus it would be difficult to differentiate the effects of second-hand smoke."

"Previous studies have shown children are exposed to third-hand smoke, more so than adults, in surprising places, for example in neonatal intensive care incubators which have clearly come from third-hand smoke," he said.

"A previous U.K. study assessing the exposure of third-hand smoke in smokers' houses suggested there would be an increased risk of cancer, possibly 1 per 1000 exposed. It is likely the risks will be higher in these settings, for example smokers' houses and cars. Another potential risk is in parents who smoke and then hold their babies. The size of the baby means it will be close to their clothing that will be emitting these toxic chemicals."